The objective of this contract is to identify and study the molecular mechanisms of action of new antitumor drugs. The protocol is structured to determine if: the drug has activity in a defined area of biochemistry or molecular biology; the observed activity is due to a direct action of the drug (rather than a secondary result); the biochemical or molecular biological activity is significantly related to its biological activity; and the activity meets the above criteria to determine the molecular details of the drug interactions. The project design if focused to distinguish primary from secondary effects and to show that they are biologically significant before proceeding to detailed studies of molecular interactions. Drugs to be studies will be selected from among those indicated by the DCT.